1. Technical Field
The present invention relates in general to an improved ball valve, and in particular to an improved valve seat and support mechanism for a ball valve.
2. Background Art
The use of in-line ball valve assemblies in subsea tree intervention tools is well known in the art. The ball valves are used to open and close a central flow passage in the assembly and are typically hydraulically actuated. In some cases, the ball valves are designed to shear coiled tubing or wireline extending through the valve in the event of an emergency.
In one type of prior art device, disclosed in U.S. Pat. No. 5,551,665, a pair of control pins slide radially inward within slots to actuate the ball between the open and closed positions. Similarly, PCT Publication No. WO 96/35857 shows and describes control pins that slide axially to accomplish the same objective. Regarding the shearing function, U.S. Pat. No. 4,160,478 illustrates a quadrant of a ball valve tool having a cutting mechanism that will cut coiled tubing in only one place. This is advantageous since a small, loose segment of tubing would otherwise be cut and remain in the assembly. The segment could then fall into the bottom of the well and create additional problems. In yet another prior art device, U.S. Pat. No. 5,284,209, describes a ball valve that shears coiled tubing in only one place due to a recess in the housing. Although all of these designs are workable, an improved ball valve assembly that provides all of the features while still providing excellent sealing capability is needed.
One embodiment of a ball valve assembly comprises a lower support, an upper seat, a spherical ball therebetween having an axial hole, and operating links for rotating the ball. The lower support has a tubular base with a spherical support surface for the ball. A recess is located in the support surface to provide relief for a wire line during cutting operations. The lower support also has a pair of guides for maintaining alignment of the ball with the supports and seat to prevent contact with the operating links.
The upper seat has a skirt with a semi-spherical inner surface that extends from the lower end of the upper portion. The inner surface of the skirt is provided with a plurality of parallel grooves for contacting an upper portion of the ball at all times. The skirt and grooves seal and ensure alignment of the ball. The grooves also assist in the retention of lubricant to reduce friction. An optional insert is located in the skirt for low pressure sealing from below and above. Finally, the skirt has a pair of openings to provide relief for the operating links, and flat structures against which the guides of the lower support may restrain rotation of the upper support.
The foregoing and other objects and advantages of the present invention will be apparent to those skilled in the art, in view of the following detailed description of the preferred embodiment of the present invention, taken in conjunction with the appended claims and the accompanying drawings.